Ultrasonic welding device and method for welding two components together

ABSTRACT

The invention relates to a ultrasonic welding device for welding two components (B 1,  B 2 ), wherein a rod-shaped first sonotrode ( 1 ) for the generation of longitudinal waves (W 1 ) is coupled on its first end (E 1 ) to a first converter ( 3 ) and on its second end (E 2 ) opposite the first end (E 1 ) to a second converter ( 5 ), wherein a first welding surface ( 9 ) is provided in the middle of the first sonotrode ( 1 ). To improve durability and to increase welding performance at the same time, the invention suggests that a second sonotrode ( 11 ) which is coupled to at least one third converter ( 13 ) and is configured as a torsion sonotrode has a second welding surface ( 15 ) arranged opposite the first welding surface ( 9 ), wherein the first ( 1 ) and the second sonotrode ( 11 ) can be moved relatively against each other such that a clamping force between the first ( 9 ) and the second welding surface ( 15 ) can be applied to the components (B 1,  B 2 ) to be connected.

The invention relates to an ultrasonic welding device as defined by thepreamble of claim 1. Furthermore, it relates to a method for welding twocomponents together.

The invention generally relates to the field of ultrasonic welding. Inparticular, it relates to the field of ultrasonic welding of metalliccomponents. In this connection, an ultrasonic oscillation is introducedparallel to a welding surface, wherein a welding force is also exertedperpendicularly at the same time. The ultrasonic oscillation makes itpossible to tear open and displace the contamination and layers of oxidewhich are usually present on metal surfaces. The direct contact with theclean surfaces resulting from this leads to a lasting, firmly bondedconnection of the metallic components.

An ultrasonic welding device as defined by the preamble of claim 1 isknown from U.S. Pat. No. 3,039,333. There, a rod-shaped sonotrode iscoupled to two converters via couplers extending radially away. Thesonotrode of this device has not proven to be especially durable.

An object of the invention is to eliminate the disadvantages of theprior art. In particular an ultrasonic welding device as durable aspossible and a method are to be specified with which especially highpower can be introduced in a welding area so that this can also be usedto weld thick-walled and/or large-surface components together.

This object is solved by the features of claims 1 and 10. Usefulembodiments of the invention result from the features of claims 2 to 9and 11.

According to the provisions of the invention, it is provided that asecond sonotrode which is coupled to at least one third converter andwhich is configured as a torsion sonotrode has a second welding surfacearranged opposite the first welding surface, and wherein the first andthe second sonotrodes are relatively moveable against each other so thata welding force can be applied between the first and the second weldingsurface to the components to be connected.—The power transferred to thecomponents to be welded can be significantly increased with thesuggested ultrasonic welding device. In particular, with this,thick-walled components can also be connected by ultrasonic welding. Afurther advantage of the suggested ultrasonic welding device is that thetorsion sonotrode can only be moved with a vertical movement, i.e.without horizontally directed movements, against the first sonotrode forwelding the components. Such a movement can be performed easily andquickly. A vertical movement unit required for this is easy andinexpensive to provide. This can increase the production speed forcomponents to be connected with each other.

According to an advantageous embodiment of the invention, the first,second and third converters are connected to the first generator. But itcan also be that the first and the second converters are connected tothe first generator and the at least one third converter is connected toa second generator. If several third converters are provided, these canalso be connected to the second generator.

The first and the second converters are operated inversely to each otherwith a phase shift of λ/2 so that the first sonotrode oscillates in alongitudinal direction. In this connection, the first converter can becoupled via a first booster and the second converter can be coupled viaa second booster to the first sonotrode. The amplitude of thelongitudinal oscillation can be adjusted by providing the boosters.

In an advantageous arrangement, the first welding surface is provided onan anvil-like projection provided in the middle of the first sonotrode.The first sonotrode is advantageously designed symmetrically, i.e., inreference to a horizontal symmetry plane, a further anvil-likeprojection is provided on the first sonotrode opposite the anvil-likeprojection. With the suggested embodiment of the first sonotrode, aparticularly great amount of power output on the components to be weldedtogether can be achieved.

According to a further embodiment of the invention, a clamping devicefor clampingly holding of at least one component to be welded isprovided on the first welding surface. The clamping device can comprisetwo clamping jaws being movable essentially perpendicular to thedirection of expansion of the longitudinal waves in the first sonotrode.The provision of such a clamping device has proven particularly good forthe connection of a braid with a connection element. The braid can, forexample, be held on the first welding surface using the clamping device.

According to an advantageous embodiment, the second sonotrode is coupledvia a third booster to the at least one third converter. The provisionof the third booster makes it possible to adjust the amplitude of thesecond sonotrode.

According to a particularly advantageous embodiment of the invention,the second welding surface is arranged eccentrically on the secondsonotrode. The “eccentrically” arranged second welding surface islocated outside an axis around which the torsion electrode oscillates.The second welding surface can be in particular a radial, outer ringsurface section on a free end of the torsion electrode. Due to this, thesecond welding surface oscillates as it were in a “longitudinal”direction. The first and the second welding surface are advantageouslyarranged relative to each other so that they oscillate in the same“longitudinal” direction. In this connection, the converters arecontrolled, however, so that the oscillations generated by the first andsecond sonotrodes are opposite each other. The second welding surfacecan also be designed in the shape of a ring.

The first sonotrode can be arranged permanently with reference to a baseand the second sonotrode can be movable relative to this in a verticaldirection. For this purpose, the second sonotrode can be attached to amovement unit with which it can be moved for the application of thewelding force against the first sonotrode.

For further increasing the power, it can be provided that the secondsonotrode is coupled to four third converters which are connected inpairs Via one common sonic transmission element, respectively, to thesecond sonotrode. In this connection, it is useful that the thirdconverters are connected to a second generator for the generation ofultrasonic waves. In case that two third converters are respectivelyarranged in pairs, they can be operated inversely to each other similarto the first and the second converters.

According to the provisions of the method of the invention, thefollowing steps are provided for the connection of two components byultrasonic welding:

Providing of the ultrasonic welding device provided by the invention,

Pressing the components to be welded between the first and the secondwelding surfaces, and

Generating ultrasonic waves by the first, second and third converters sothat the components to be welded are welded together.

According to an embodiment of the alternate version of the method, thefirst and the second converters—on the one hand—can be operated in afirst cycle and the third converters—on the other hand—can be operatedin a second consecutive cycle. But it is also possible to operate thefirst, second and third converters simultaneously.

The invention will now be described in more detail using an examplebased on the drawing. It is shown:

FIG. 1 a view in perspective of an ultrasonic welding device,

FIG. 2 a side view as per FIG. 1 and

FIG. 3 a sectional view as per intersecting line A-A in FIG. 2.

The figures show an ultrasonic welding device for welding of twometallic components B1, B2, for example, two braids having a diameter ofmore than 8 mm. A rod-shaped first sonotrode 1 is connected on its firstend E1 via interposition of a first booster 2 to a first converter 3. Asecond end E2 of the first sonotrode 1 is connected to a secondconverter 5 via interposition of a second booster 4. The arrangement issymmetrical with regard to a median plane. The median plane correspondsto intersecting line A-A in FIG. 2. The first converter 3 and the secondconverter 5 can be operated together with a first generator 6. Due tothis, the longitudinal waves W1 are impressed on the first sonotrode 1.

As is particularly shown in FIGS. 2 and 3, the first sonotrode 1 has ananvil-like projection 7 in its middle and a symmetrical counterprojection 8 located opposite. The projection 7 is provided with an evenwelding surface 9 on which the metallic components B1, B2 to be weldedare placed. Reference sign 10 denotes clamping jaws of a (not shown inmore detail here) clamping device which can be moved back and forthperpendicularly to the direction of expansion of the longitudinal wavesW1.

To generate particularly high powers, a second sonotrode arrangement isprovided instead of an anvil in the exemplary embodiment shown. In thisconnection, a second sonotrode 11 is coupled via a third booster 12 totwo third converters 13 arranged in pairs, respectively. Two thirdconverters 13 are respectively coupled together via a transmissionelement 14. The transmission elements 14 are tangentially coupled to atorsion rod 16 extending from the third booster 12 in an arrangementopposite each other.

Two third converters 13 connected with each other via a transmissionelement 14 can—similar to the first converter 3 and the second converter5—be operated inversely to each other with a phase shift of λ/2 so thatthe transmission element 14 oscillates in a longitudinal direction. Theopposite pair of third converters 13 is in turn designed so that itoscillates in the opposite direction from the other pair so that thetorsion waves W2 are impressed on the second sonotrode 11.

FIG. 3 shows a second welding surface designated as reference sign 15which is provided eccentrically on the second sonotrode 11.

The function of the ultrasonic welding device is as follows:

To weld two braids B1, B2 made of aluminum, for example, these areplaced on top of each other on the first welding surface 9. Then theclamping jaws 10 are moved against each other and the braids B1, B2 ontop of one another are fixated on the first welding surface 9. Then thesecond sonotrode 11 is moved vertically and placed on the firstsonotrode 1 in such a manner that the first 9 and the second weldingsurfaces 15 are located approximately opposite each other. A specifiedwelding force or a specified pressure is applied to the braids B1, B2which are located on top of each other.

Then the first generator 6, for example, is operated in such a mannerthat—on one hand—the first converter 3 and the second converter 5 and—onthe other hand—the third converters 13 are operated alternately. But itcan also be that the first converter 3 and the second converter 5 areoperated together by a first generator 6 and the third converters 13 areoperated by a second generator (not shown here).

The first 6 and/or the second generators can have a power in the rangeof 15 to 20 KW. It has been shown to be useful to operate sonotrodes 1,11 with a frequency in the range of 15 and 20 kHz. In this connection,amplitudes between 20 and 150 μm are generated on welding surfaces 9,15.

Although the preceding exemplary embodiment has been discussed based onthe connection of two metallic components, the suggested ultrasonicwelding device is also suitable for connecting components made ofplastic.

LIST OF REFERENCE SIGNS

-   1 First sonotrode-   2 First booster-   3 First converter-   4 Second booster-   5 Second converter-   6 First generator-   7 Projection-   8 Counter projection-   9 First welding surface-   10 Clamping jaws-   11 Second sonotrode-   12 Third booster-   13 Third converter-   14 Transmission element-   15 Second welding surface-   16 Torsion rod-   B1 First component-   B2 Second component-   E1 First end-   E2 Second end-   W1 Longitudinal wave-   W2 Torsion wave

1. Ultrasonic welding device for welding two components (B1, B2),wherein a rod-shaped first sonotrode (1) for the generation oflongitudinal waves (W1) is coupled on its first end (E1) to a firstconverter (3) and on its second end (E2) opposite the first end (E1) toa second converter (5), wherein a first welding surface (9) is providedin the middle of the first sonotrode (1), characterized in that a secondsonotrode (11) which is coupled with at least one third converter (13)and which is configured as a torsion sonotrode has a second weldingsurface (15) arranged opposite the first welding surface (9), whereinthe first sonotrode (1) and the second sonotrode (11) are relativelymovable against each other such that a welding force can be appliedbetween the first (9) and the second welding surface (15) to thecomponents (B1, B2) to be connected.
 2. Ultrasonic welding device asdefined in claim 1, wherein the first (3), second (5) and thirdconverters (13) are connected to at least one first generator (6) forthe generation of ultrasonic waves.
 3. Ultrasonic welding device asdefined in claim 1, wherein the first (3) and the second converters (5)are connected to the first generator (6) and the at least one thirdconverter (13) is connected to a second generator.
 4. Ultrasonic weldingdevice as defined in claim 1, wherein the first converter (3) is coupledvia a first booster (2) and the second converter (5) is coupled via asecond booster (4) to the first sonotrode (1).
 5. Ultrasonic weldingdevice as defined in claim 1, wherein the first welding surface (9) isprovided on an anvil-like projection (7) provided in the middle of thefirst sonotrode (1).
 6. Ultrasonic welding device as defined in claim 1,wherein a clamping device for clampingly holding of at least one of thecomponents (B1, B2) to be welded is provided on the first weldingsurface (9) which comprises two clamping jaws (10) being movableessentially perpendicular to the direction of expansion of thelongitudinal waves (W1) in the first sonotrode (1).
 7. Ultrasonicwelding device as defined in claim 1, wherein the second sonotrode (11)is coupled via a third booster (12) to the at least one third converter(13).
 8. Ultrasonic welding device as defined in claim 1, wherein thesecond welding surface (15) is arranged eccentrically on the secondsonotrode (11).
 9. Ultrasonic welding device as defined in claim 1,wherein the second sonotrode (11) is coupled to four third converters(13) which are connected in pairs via one common sonic transmissionelement (14), respectively, to the second sonotrode (11).
 10. Method forconnecting two components (B1, B2) by ultrasonic welding comprising thefollowing steps: Providing of the ultrasonic welding device as definedin claim 1, Pressing the components (B1, B2) to be welded between thefirst (9) and the second welding surface (15), and Generating ultrasonicwaves by the first (3), second (5) and third converters (13) so that thecomponents (B1, B2) are welded together.
 11. Method as defined in claim10, wherein the first (3), second (5)—one the one hand—and thirdconverters (13)—on the other hand—are operated simultaneously or oneafter the other.